The invention relates to a lens barrel for containing a movable lens therein.
Taking lens of a camera, projection lens of a slide or cine projector, or most of objectives which comprise a plurality of single lenses contains a movable lens within its barrel for purpose of varying magnification or focussing. A mechanism for holding such a movable lens in the lens barrel comprises an outer sheath having a helical groove or a guide groove of any other configuration formed in its inner peripheral surface, and an inner sheath fitted into the outer sheath in a rotatable manner and formed with axially extending slits which are open at one end thereof. A frame which retains a movable lens is fitted into the inner sheath so as to be slidable therein in the axial direction, with tabs which extend radially outward from the periphery of the frame passing through the slits in the inner sheath into engagement with the guide groove in the outer sheath. By turning either one of the outer and the inner sheath while holding the other in a stationary manner, the points of intersection between the slits and the guide groove, and hence the radial tabs as well as the lens frame integral therewith undergo an axial movement.
It is necessary to prevent a relative axial movement between the both sheaths while permitting a relative rotation therebetween. This end is achieved in the prior art by using a separate member which retains the both sheaths in a manner to permit a relative rotation therebetween. By way of example, an annular connection member is employed which is threadably engaged with the end of the outer sheath and which is provided with an inwardly directed flange, which bears against the end of the inner sheath.